Commit 31f251d4 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
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KVM: SVM: Signal AVIC doorbell iff vCPU is in guest mode 



Signal the AVIC doorbell iff the vCPU is running in the guest.  If the vCPU
is not IN_GUEST_MODE, it's guaranteed to pick up any pending IRQs on the
next VMRUN, which unconditionally processes the vIRR.

Add comments to document the logic.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20211208015236.1616697-11-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c3e8abf0

arch/x86/kvm/svm/avic.c

+20 −2
Original line number Diff line number Diff line
@@ -672,9 +672,22 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec) 
		return -1;



	kvm_lapic_set_irr(vec, vcpu->arch.apic);



	/*

	 * Pairs with the smp_mb_*() after setting vcpu->guest_mode in

	 * vcpu_enter_guest() to ensure the write to the vIRR is ordered before

	 * the read of guest_mode, which guarantees that either VMRUN will see

	 * and process the new vIRR entry, or that the below code will signal

	 * the doorbell if the vCPU is already running in the guest.

	 */

	smp_mb__after_atomic();



	if (avic_vcpu_is_running(vcpu)) {

	/*

	 * Signal the doorbell to tell hardware to inject the IRQ if the vCPU

	 * is in the guest.  If the vCPU is not in the guest, hardware will

	 * automatically process AVIC interrupts at VMRUN.

	 */

	if (vcpu->mode == IN_GUEST_MODE) {

		int cpu = READ_ONCE(vcpu->cpu);



		/*
@@ -688,8 +701,13 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec) 
		if (cpu != get_cpu())

			wrmsrl(SVM_AVIC_DOORBELL, kvm_cpu_get_apicid(cpu));

		put_cpu();

	} else

	} else {

		/*

		 * Wake the vCPU if it was blocking.  KVM will then detect the

		 * pending IRQ when checking if the vCPU has a wake event.

		 */

		kvm_vcpu_wake_up(vcpu);

	}



	return 0;

}